In 2008 one half of the Nobel Prize in Physiology and Medicine went to Harald zur Hausen, Professor Emeritus at the German Cancer Research Centre, for his discovery of the human papilloma viruses (HPV) that cause cervical cancer. The functioning of this virus proved to be both a scientific theoretical breakthrough as well as leading to effective vaccines.
Background of Cervical Cancer Research
Cervical cancer is the second most common cancer among women. It had long been thought that this was caused by a sexually transmitted agent such as the herpes simplex type 2 virus (HSV-2). Although there was some experimental evidence to support this, Harald zur Hausen failed to find the HSV-2 DNA inside actual cancer cells. He had used the same technique to successfully identify other viruses such as the Epstein-Barr virus, so zur Hausen turned his attention to another possible agent, the human papilloma virus (HPV).
Going Against the Orthodox Theory
The HPV virus was well known in connection with genital warts but the prevailing theory at the time was that if a tumour cell became cancerous then the cancer-producing (oncogenic) virus would reveal itself by DNA replication and the production of virus particles. Contrary to this, zur Hausen postulated that the viral DNA could exist in a dormant non-productive state within the tumour cells and therefore the only way to find it was to search specifically for the viral DNA code inside the genome of the tumour cells. His motivation was that he had,”surveyed the literature and found a number of anecdotal reports on malignant conversion of genital warts.”
Discovery of HPV16
Harald zur Hausen pursued this idea for over 10 years by searching for different HPV types, a search made difficult by the fact that only parts of the viral DNA were integrated into the host genome. He found novel HPV-DNA in cervix cancer biopsies, and thus discovered the new, tumour-producing HPV16 type in 1983. In 1984, he cloned HPV16 and HPV18 from patients with cervical cancer. The HPV types 16 and 18 were consistently found in about 70% of cervical cancer biopsies throughout the world.
From Discovery to Vaccines
The global public health burden attributable to human papilloma viruses is considerable. More than 5% of all cancers worldwide are caused by persistent infection with this virus. Infection by HPV is the most common sexually transmitted agent, afflicting 50-80% of the population. Of the more than 100 HPV types now known, about 40 infect the genital tract, and 15 of these put women at high risk of developing cervical cancer. In addition, HPV is found in some other sexually transmitted cancers. Human papilloma virus can now be detected in 99.7% of women with confirmed cervical cancer, affecting some 500,000 women per year. Harald zur Hausen made HPV16 and 18 available to the scientific community and vaccines were ultimately developed that provide over 95% protection from infection.
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